import tensorflow as tf


class Controller(object):
    def __init__(self, *args, **kwargs):
        raise NotImplementedError("Abstract method.")

    def _build_sample(self):
        raise NotImplementedError("Abstract method.")

    def _build_greedy(self):
        raise NotImplementedError("Abstract method.")

    def _build_trainer(self):
        raise NotImplementedError("Abstract method.")
